function Hv = h(alpha, beta)
k = [cos(alpha)*cos(beta);
    cos(alpha)*sin(beta);
    sin(alpha)];

r{1}=[1/4 0 0];
r{2}=[-1/4 0 0];

phi = nan(2,1);

for i=1:2
    phi(i)=2*pi*r{i}*k;
end

Hv = exp(1i*phi);
end